The safety-pin-wearing left is aghast at the realization that President Donald Trump could actually follow through on his promise to "cancel every unconstitutional executive action, memorandum and order issued by President Obama" on his first day in office. He should do it.

Every president reverses some executive actions of the previous president. After President Barack Obama took office in 2009, he revoked a series of executive orders issued by President George W. Bush - including Bush's executive order barring federal funding for embryonic stem-cell research; his executive order implementing the Mexico City Policy, which bars funding for international groups that provide abortions; his executive order interpreting the Geneva Conventions with regard to the CIA's detention of captured terrorists; and several Bush executive orders limiting the power of labor unions in dealing with federal contractors, among many others. Obama also used executive orders to reverse Bush's terrorist interrogation policy and order the closure of the U.S. military prison at Guantanamo Bay.

Obama's actions were not unprecedented. Bush not only reversed executive orders of his predecessor, Bill Clinton, but in 2002 he actually withdrew the U.S. from a treaty Clinton had signed - the Rome Statute creating the International Criminal Court.

The reason Obama's legacy is so vulnerable today is that the 44th president relied more on executive actions - issuing not only executive orders, but also a record number of rules, regulations and agency directives to legislate around Congress and impose his agenda.

After he lost control of the Senate in 2014, Obama announced at his first Cabinet meeting: "We're not just going to be waiting for legislation. . . . I've got a pen and I've got a phone. And I can use that pen to sign executive orders and take executive actions and administrative actions that move the ball forward." On immigration, when Obama could not pass his immigration reform to provide amnesty for entire categories of people not here legally, he tried to impose it on the American people though unlawful executive action - a move The Washington Post's editorial board called a "massive unilateral act" that "flies in the face of congressional intent."

When he could not pass his cap-and-trade bill, he used the Clean Air Act to impose it by executive action, twisting the meaning of the law in a manner that even the New York Times said was "stretching the intent of a law decades old and not written with climate change in mind." He took executive actions on everything from gun control and financial regulation to health care and transgender bathrooms.

Now Trump may use his pen and phone to reverse many of Obama's executive actions. And the lame-duck president can hardly complain. If you rule by executive fiat, then you should not be surprised if the next executive undoes your fiats.

Some of Obama's executive actions will be easy to repeal. Trump can, with the stroke of his pen, reverse Obama's orders to close Guantanamo Bay. He can also scrap the Paris Agreement on climate change that Obama signed in September, which is completely non-binding, by simply announcing that the United States will not fulfill its obligations. Obama's executive actions under Title IX denying due process to those accused of sexual assault and requiring schools to allow transgender students to bathrooms that do not match their biological gender are easily reversed. They were issued as guidance that do have any force of law at all, yet the Education Department is enforcing them as if they did - threatening universities with loss of funds if they don't comply. Repealing those won't take anything more than Trump's new education secretary simply saying, "Never mind."

Plus, Obama set a land speed record for major regulations - defined as regulations costing the economy $100 million or more - imposing more than 600 since taking office. Many of those will be difficult to do undo, because they were issued through notice and comment by the agencies. For instance, the Clean Power Plan from the Environmental Protection Agency, which Trump has promised to scrap, can't be undone with a stroke of the pen. The EPA would have to formally revoke it, which could itself lead to litigation. That's why it's so important for Trump to put good justices on the Supreme Court, so they can not only strike down illegal regulations but also set precedents that will be binding on future presidents as well.

If Trump really wants to shake up Washington, he should issue a single executive order on Day One repealing all of Obama's executive orders. Then, he could go back and decide which, if any, to reinstate.

It's not just Obama's executive actions that will soon be reversed. His signature legislative achievement, Obamacare, is headed for repeal - and he has no one to blame but himself. Obama passed his health-care reform without any Republican buy-in or any effort to reach bipartisan consensus. He controlled both houses of Congress, and so he imposed his will over the objection of every single Republican. Now that Republicans control both Congress and the White House, they have no incentive to preserve the law.

From legislation to executive action, the lesson is clear: The value of bipartisan compromise is not just about optics. If you build consensus, then your actions will last. But if you impose your agenda on an unwilling country, it is going to get repealed or reversed when the other party comes to power.

There is wisdom in the scriptural admonition to "be like a wise man who built his house on the rock" instead of the "foolish man who built his house on the sand. And the rain fell, and the floods came, and the winds blew and beat against that house, and it fell, and great was the fall of it."

Obama built his legacy on the sand of unilateralism, instead of the rock of bipartisan consensus. And great will be the fall of it come Jan. 20, 2017.

Previously:•11/027/16: Get ready for four more years of Clinton scandals
•10/27/16: WikiLeaks is exposing Clinton's duplicity, but it's no hero
•10/16/16: Hillary Clinton is a threat to religious liberty
•09/20/16: Hillary Clinton tells dreadful lies
•09/14/16: Bill Clinton's terrorism strategy led to 9/11. Hillary Clinton's is the exact same thing
•07/28/16: The Dems' well-deserved WikiLeaks blowback
•07/18/16: We were warned. Get ready for more terror attacks, folks
•07/08/16: The FBI should release the memo
•06/21/16: Trump neutralizes Dems' attacks by adopting their positions
•06/16/16: Obama still in denial even after losing life and death game of connect-the-dots
•04/12/16: What Trump can learn from Reagan and the '76 delegate fight
•04/06/16: Gaffes show Trump is the left-wing caricature of a conservative
•03/18/16: Stop blaming Trump supporters for campaign violence
•02/22/16: Hey, Bernie: You're blowing it by refusing to attack Hillary over her scandals
•02/02/16: Political establishment can learn a few things from hockey's all-star enforcer
•01/26/16: Hillary's email excuses are falling apart
•12/15/15: How Rubio is quietly killing ObamaCare
•10/21/15: Yes, George W. Bush kept us safe
•10/14/15: Finding a consensus conservative for the GOP